They are on opposite ends of the political spectrum, but Northampton’s Joseph B. Tarantino and South Hadley’s Robert Salthouse share one thing in common.

They’re willing to go to great lengths to see their choice for president elected today — all the way to the doors of voters in key battleground states that may end up deciding the election.

Tarantino, chairman of the Northampton City Republican Committee, returned Sunday after two weeks of door-knocking for Republican Mitt Romney in Cincinnati. The Buckeye State with its 18 electoral votes is one of a handful of swing states that political prognosticators believe could turn the tide in the election.

“I believe the conventional wisdom that who wins Ohio is going to win the overall election, and so I decided that if I could contribute in any small way, I would,” said Tarantino, who has been fired up about the election since attending the Republican National Convention in Florida in August.

Salthouse agrees, albeit it from the left side of the aisle. That’s why he and other local supporters of President Barack Obama, including Salthouse’s wife, Bobbie, have spent their weekends canvassing neighborhoods in Keene, N.H. With four electoral votes, New Hampshire may be small, but it is a key state.

“We both just feel it’s really important to get Obama re-elected,” Salthouse said. “We wanted to do more than just vote and New Hampshire is a swing state. We wanted to see if we could help.”

There’s a stark contrast between living in Massachusetts, where the presidential race is strongly in Obama’s favor, and visiting battleground states like Ohio and New Hampshire, these volunteers agree.

In the two weeks he spent in Ohio with his girlfriend’s family, Tarantino said political advertisements dominated every commercial break, flooded every mailbox and dotted hundreds of lawns. Media coverage led every newscast and front page. Tarantino’s other relatives in Florida and Virginia are also being inundated.

“You’re totally immersed in politics,” Tarantino said. “When you’re here (in Massachusetts), you don’t realize the frenzy that’s going on that people in these states are dealing with.”

Then there are the volunteers who work at phone banks and knock on doors. Tarantino said he met other Romney backers canvassing Ohio like himself who hailed from Texas, Wyoming and other uncontested states.

“I met people from all over the country and I think they thought that it was odd that I came from a very blue state where most of the Romney volunteers had come from very red states,” Tarantino said.

Salthouse said he also met volunteers who flocked to the Keene area from throughout New England to remind the mostly Democratic voters to get to the polls today.

During two visits to the Granite State in recent weeks, Salthouse and his wife visited with college students in downtown Keene and spent time in a rural area just north of the city.

These types of canvass excursions have been taking place for weeks, with separate groups traveling from Northampton, Amherst, South Hadley and other Valley communities seeking to make a difference in this year’s race.

He said residents there are used to the regular visits from volunteers like himself, and many are tired of being canvassed.

“They’re definitely being wooed,” Salthouse said.

Tarantino spent most of his time in Anderson Township, a section of Cincinnati about 15 minutes from downtown. Rather than working the phones, he preferred rubbing elbows with Ohioans in person. So Romney’s campaign gave him a list of undecided and other “low-intensity” Republican voters who were leaning toward Romney.

Over a 10-day period, Tarantino knocked on 320 doors, dropping off fliers and talking to voters about why he believes Romney is the best choice for president. He also attended a Romney rally and was interviewed about his experience on a local radio station.

“I’m reasonably confident that I closed the deal for Mitt Romney with six undecided voters after having talked to them,” said Tarantino, who met Romney in 2004 during an unsuccessful bid for state representative.

While he was ready to talk about the differences between Romney and Obama on the economy, health care, the military and other topics, one young Catholic woman’s quandary forced Tarantino to change course shortly after she greeted him.

She told Tarantino that Romney simply wasn’t pro-life enough. The Northampton Republican asked her to think in practical terms when comparing the candidates, noting that Romney’s running mate, Paul Ryan, is more in line with her beliefs and that she would not be compromising her position by voting for Romney.

“I think I convinced her with that argument,” he said. “You really have to be quick on your feet.”

He said many of the people he spoke with were Romney supporters, but one voter told Tarantino he had no interest in casting a ballot.

“Some of these unmotivated voters, I told them I envy their position here because your vote is going to count more than most people in the country,” Tarantino said.

As for a prediction, Salthouse is confident he’ll like the election’s outcome late tonight.

“I think Obama is going to win,” he said.

Tarantino said he’s feeling much better today about Romney’s chances than he did a few weeks ago.

“I think Romney is going to win Ohio and I think he’s going to win the election,” Tarantino said. “I originally thought it wasn’t going to be close.”

If that happens, it will be the best birthday gift Tarantino will ever receive. He turns 48 today.